The Spring Framework: Overview and Setup

Transcription

1 2009 Marty Hall The Spring Framework: Overview and Setup Originals of Slides and Source Code for Examples: Customized Java EE Training: Servlets, JSP, Struts, JSF/MyFaces/Facelets, Ajax, GWT, Spring, Hibernate/JPA, Java 5 & 6. Developed and taught by well-known author and developer. At public venues or onsite at your location Marty Hall For live Java training, please see training courses at coreser com/ Servlets, JSP, Struts, ts JSF, Ajax, GWT, Java 5, Java 6, Spring, Hibernate, JPA, and customized combinations of topics. Taught by the author of Core Servlets and JSP, More Servlets and JSP, and this tutorial. Available at public venues, Customized or customized Java EE Training: versions can be held on-site at your Servlets, JSP, Struts, JSF/MyFaces/Facelets, Ajax, GWT, Spring, Hibernate/JPA, Java 5 & 6. organization. Contact hall@coreservlets.com for details. Developed and taught by well-known author and developer. At public venues or onsite at your location.

2 Agenda What is Spring? And why use it? Main Spring modules Dependency injection i AOP Configuring apps to use Spring And Eclipse plugin support Simple example Marty Hall Overview of Spring Customized Java EE Training: Servlets, JSP, Struts, JSF/MyFaces/Facelets, Ajax, GWT, Spring, Hibernate/JPA, Java 5 & 6. Developed and taught by well-known author and developer. At public venues or onsite at your location.

3 What is Spring? 7 Spring is a framework with many modules To simplify many different Java EE tasks Core module: dependency injection Lets you define an XML file that specifies which h beans are created and what their properties are Simplifies OOP by promoting loose coupling between classes. Also called Inversion of Control (IoC) Small example shown in this lecture; details in next lecture Second most important module: AOP Aspect Oriented Programming refers to the ability to add side effects to a class method calls without modifying the class source code Lets you separate business logic from system services Why Spring? Disenchantment with EJB Too complicated Objects were technology-specific: tied to EJB Hard to test in isolation Basic Spring philosophy Avoid tight coupling among classes Approaches to support this philosophy Use POJOs (Plain Old Java Objects) Add enterprise services declaratively Use Spring to obtain object instances and to manage their lifecyle. l Don t make Spring-dependent d classes. However, annotations partially violate this principle 8

4 Spring Modules 9 From Spring in Action, 2 nd Edition by Craig Walls Use of Spring in Industry Claims to compile data from most major jobs sites Data through 12/

5 2009 Marty Hall Installation and Setup Customized Java EE Training: Servlets, JSP, Struts, JSF/MyFaces/Facelets, Ajax, GWT, Spring, Hibernate/JPA, Java 5 & 6. Developed and taught by well-known author and developer. At public venues or onsite at your location. Downloading 12 Choose latest released version as of 12/2008 Choose Community Download This is free and open source There is also Enterprise version that comes with paid support Choose version with dependencies Includes required and optional JAR files, documentation, and samples You only have to use the JAR files you want, so there is no harm in downloading the full version spring-framework with-dependencies.zip as of 12/08 Alternative: download spring-blank.zip Eclipse project with two required JAR files, blank applicationcontext.xml, and Eclipse Spring IDE nature From coreservlets.com; see link on title page of this tutorial.

6 Installation 13 Unzip into directory of your choice I will refer to this later as spring-install i To add Spring capabilities to projects Simple Java project Add two JAR files to project class path spring-install/dist/spring.jar spring-install/lib/jakarta-commons/commons-logging.jar Create empty bean definition file to use as a starting point Usually placed in top-level of class path: src/applicationcontext.xml Simple example given in this lecture Dynamic Web Project Add two JAR files to WEB-INF/lib spring-install/dist/spring.jar spring-install/lib/jakarta-commons/commons-logging.jar Place starting-point bean definition file in WEB-INF Declare listener that loads the bean definition file at app startup Simple example given in next lecture Documentation Online docs Rf Reference documentation API in JavaDoc Tutorials and setup guides p p Documentation for Spring Eclipse plugin Books Spring Recipes by Gary Mak (APress) Covers Spring 2.5 Spring in Action by Craig Walls (Manning) Covers Spring

7 IDE Support for Spring 15 Spring IDE Free, open source, Eclipse only. Used in these tutorials. Skyway Builder Commercial Eclipse plugin for Spring and Hibernate Others for Eclipse Search Eclipse Plugin Central. Several new ones listed. Other IDEs MyEclipse Has their own Spring support. com/ Intellij IDEA Has their own Spring support. Spring IDE: Eclipse Plugin for Spring Idea Optional plugin adds many useful Spring-aware features to Eclipse. Highly recommended for Eclipse users. Installation Help Software Updates Available Software Add Site Enter Select both the springide.org site and the automatically-created site for AspectJ support Click Install 16

8 Making a New Spring Project Make new Java project New Project Java Java Project 2. Add Spring IDE Eclipse support R-click project, Spring Tools Add Spring Project Nature For regular Java projects (not Dynamic Web Projects) you can combine the above two steps by doing New Project Spring Spring Project. You can still use Spring even if you don t have Spring IDE. Adding the project nature just makes Eclipse smarter about editing and graphically displaying certain files. 3. Add spring.jar and commons-logging.jar Details on next slide 4. Put an empty bean definition file in src Details on upcoming slide Adding JAR Files to Project Required JAR files spring.jar (from dist folder) If disk space is critical, you can choose among many smaller JAR files. But simplest to just use spring.jar. commons-logging.jar (from lib/jakarta-commons ) Putting JAR files in class path Make a new project directory (e.g., lib ) Copy spring-install/dist/spring.jar and spring-install/lib/jakarta-commons/commons-logging.jar to the lib folder. R-click on project, Properties Libraries Add JARs Then point at lib/spring.jar and lib/commons-logging.jar For Dynamic Web Projects Instead of above steps, copy JARs to WEB-INF/lib 18

9 Making a Bean Definition File 19 Idea XML file defines objects (beans) and gives them names. Java code will load file and refer to objects by name. File is most commonly loaded relative to the class path, so is typically placed in src folder File can have any name Common choices are beans.xml and applicationcontext.xml Creating with Spring IDE R-click on src folder New Other Spring Spring Bean Definition iti Choose a name and hit Finish Sample Bean Definition File Starting point file <?xml version="1.0" encoding="utf-8"?> <beans xmlns=" xmlns:xsi=" xsi:schemalocation=" <!-- Your entries will go here --> </beans> 20 Spring IDE is not required This file can be created and edited manually Grab one from the samples that come with Spring Make sure it does not refer e to fancy features es you are not using yet Delete everything between <beans > and </beans> Or, take the empty one from spring-blank

10 The spring-blank Project 21 Preconfigured Eclipse project Standard Java project with Spring Project Nature But works with or without Spring IDE plugin spring.jar and commons-logging.jar in lib folder And with those two JARs added to build path Empty applicationcontext.xml file in src folder Usage R-click project, Copy R-click in Project Explorer, Paste, give new name Download from coreservlets.com com/spring Import into Eclipse with File Import General Existing Projects into Workspace 2009 Marty Hall Simple Spring Example Customized Java EE Training: Servlets, JSP, Struts, JSF/MyFaces/Facelets, Ajax, GWT, Spring, Hibernate/JPA, Java 5 & 6. Developed and taught by well-known author and developer. At public venues or onsite at your location.

11 Goal: Loose Coupling 23 Geometric analysis You have a program that computes areas for various collections of shapes. You want to avoid code that depends on any particular type of shape, since the varieties of shapes keep changing. Strategy Define interface or abstract class No dependencies on Spring Make concrete implementations of the interface No dependencies on Spring Declare specific concrete object in bean definition file Load bean definition file and get instance (driver class) No dependency on specific concrete type Making Spring Project 24 From scratch File New Project Spring Spring Project Or, if no Spring IDE, File New Java Java Project Named project spring-intro R-clicked on project, made new folder called lib Copied spring-install/dist/spring.jar and spring-install/lib/jakarta-commons/commons-logging.jar to lib R-clicked on project, Properties Libraries Add JARs Then pointed at lib/spring.jar and lib/commons-logging.jar R-clicked src folder and New Other Spring Spring Bean Definition If no Spring IDE, copied sample applicationcontext.xml file By copying existing project Copied spring-blank Renamed copy to spring-intro

12 Interface package coreservlets; public interface Shape { public double getarea(); Notes No imports of Spring packages No ties in any way to Spring Code that only uses the area (or inherited methods like tostring) should refer only to Shape But interfaces cannot be used everywhere: code that uses more specific info (e.g., the radius of a Circle that implements Shape) will need to use concrete type 25 Concrete Class: Rectangle public class Rectangle implements Shape { private double length, width; public Rectangle() { The driver class will use only getarea and methods inherited from Object, so will refer to Shape, not Rectangle. The bean definition in the upcoming applicationcontext.xml file will not specify any constructor arguments. So, the zero-arg constructor will be used. public Rectangle(double length, double width) { setlength(length); setwidth(width); 26

13 Rectangle (Continued) public double getlength() { return(length); public void setlength(double length) { this.length = length; public double getwidth() { return(width); The bean definition in the upcoming applicationcontext.xml file will refer to the length and width properties. That really means to call setlength and setwidth. 27 public void setwidth(double width) { this.width = width; public double getarea() { return(length * width); Concrete Class: Circle public class Circle implements Shape { private double radius = 1.0; public Circle() { public Circle(double e radius) { setradius(radius); public double getradius() { return(radius); The bean definition in the upcoming applicationcontext.xml file will supply a number as a constructor argument. So, this constructor will be used. 28 public void setradius(double radius) { this.radius = radius; public double getarea() { return(math.pi * radius * radius);

14 Bean Definition File: applicationcontext.xmlxml <?xml version="1.0" encoding="utf-8"?> <beans xmlns=" xmlns:xsi=" xsi:schemalocation=" <bean id="shape1" class="coreservlets.rectangle"> <property name="length" value="10"/> <property name="width" value="20"/> </bean> <bean id="shape2" class="coreservlets.circle"> <constructor-arg value="10"/> </bean> </beans> Call new Rectangle(), then setlength(10) and setwidth(20). Associate the instance with the name shape1. Call new Circle(10). Associate the instance with the name shape2. 29 Driver Class package coreservlets; import org.springframework.context.*; import org.springframework.context.support.*; public class ShapeTest { public static void main(string[] args) { ApplicationContext context = new ClassPathXmlApplicationContext ("/applicationcontext.xml"); Shape shape1 = (Shape)context.getBean("shape1"); printinfo(shape1); Shape shape2 = (Shape)context.getBean("shape2"); printinfo(shape2); File is in src, which is top level of class path. Names as given in applicationcontext.xml. 30

15 Driver Class (Continued) private static void printinfo(shape shape) { System.out.printf("Area of %s is %.2f%n", shape.getclass().getsimplename(), shape.getarea()); Since type is declared as Shape, use only methods defined in the interface (getarea) or inherited from Object (getclass). 31 Output Rectangle with area of Circle with area of

16 2009 Marty Hall Wrap-up Customized Java EE Training: Servlets, JSP, Struts, JSF/MyFaces/Facelets, Ajax, GWT, Spring, Hibernate/JPA, Java 5 & 6. Developed and taught by well-known author and developer. At public venues or onsite at your location. Summary 34 Why Spring? Spring promotes loose coupling among classes, isolating one class from changes in another. Using Spring in your apps Add spring.jar and commons-logging.jar to class path Put a bean definition file in your class path Approach Define interface or abstract class Make concrete implementations of the interface Declare specific concrete object in bean definition file <bean id="somename" class="package.class"> </bean> Use property or constructor-arg Load bean definition file and get instance

17 2009 Marty Hall Questions? Customized Java EE Training: Servlets, JSP, Struts, JSF/MyFaces/Facelets, Ajax, GWT, Spring, Hibernate/JPA, Java 5 & 6. Developed and taught by well-known author and developer. At public venues or onsite at your location.